A heavily planted tank can handle a good sized bio-load from the get go. The plants will eat through that ammonia and the other products of the cycle at a rate.
When I start a new tank and it is heavily planted I usually just put all the fish I want to keep in there at the start. After 8 years of doing it that way I have yet to lose a single fish or detect ammonia or nitrite. I even need to add nitrates so there is none of that either!
The more you see the amazing filters plants are the more you wonder how we ever survived before!!